I put the pack in the mentionned folder and i got the same error. When enabling logs (debug) i only got these 3 lines :
[WARN] [Shaders]: Could not read shader preset in #reference line: “\NAS\Launchbox\LaunchBox\Emulators\RetroArch\shaders\shaders_slang\shaders_slang\bezel\Mega_Bezel\Presets\Base_CRT_Presets\MBZ__1__ADV__GDV.slangp”.
[ERROR] [GLCore]: Failed to create preset: “\NAS\Launchbox\LaunchBox\Emulators\RetroArch\shaders\shaders_slang\bezel\Mega_Bezel\Presets\Advanced\Atari_2600\2600-[ADV]-[Guest]-[Bezel].slangp”.
[ERROR] [GLCore]: Failed to create filter chain: “\NAS\Launchbox\LaunchBox\Emulators\RetroArch\shaders\shaders_slang\bezel\Mega_Bezel\Presets\Advanced\Atari_2600\2600-[ADV]-[Guest]-[Bezel].slangp”. Falling back to stock.